The present subject matter relates to techniques and equipment, such as, an apparatus and a method thereof for supplying operation voltage/current for use in a high-voltage discharge lamp, which can be applied into a projection-type display apparatus, for example, a liquid crystal projector, etc., and in particular, it relates to a lamp operation controller and a controlling method thereof, for obtaining a stable light (i.e., an output) irrespective of changes or variation with the passage of time in the high-pressure discharge lamp.
Conventionally, a high-pressure discharge lamp, such as, a metal-halide lamp, a high-pressure mercury lamp, etc., for example, is used, as a light source of the projection-type display apparatus, such as, the liquid crystal display projector, etc., from a reason of easily obtaining a light near to a spot-like light source, as well as, with high conversion efficiency. Also, for the purpose of lighting such the high-pressure discharge lamp, there is applied a discharge lamp lighting apparatus for exclusive use thereof, to supply voltage and current necessary for the lighting. In recent years, a method is proposed or disclosed of controlling the discharge lamp lighting apparatus with an aid of a microcomputer, thereby to keep electric power to be constant through calculation of the consumption of electric power, as is described in Japanese Patent Laying-Open No. Hei 5-74583 (1993), and Japanese Patent Laying-Open No. Hei 8-8076 (1996), for example.
The structures of the high-pressure discharge lamp are already known from, for example, Japanese Patent Laying-Open for International Application No. 2000-515311 (2000), etc. And, to the high-pressure discharge lamp are applied an alternating operation voltage and also an alternating operation current, both being in a rectangular waveform, as is already known by, Japanese Patent Laying-Open for International Application No. 2002-534766 (2002), Japanese Patent Laying-Open for International Application No. 2002-532866, Japanese Patent Laying-Open No. 2002-15883 (2002), U.S. Pat. No. 5,608,294, for example. Also, pulse-like current is supplied, for the purpose of reducing generation of fluctuation on arc voltage and/or flickers due to wear of electrodes accompanying the discharge, etc., into a specific time portion of the lamp current, having a rectangular shape or a predetermined shape changing the polarity thereof, alternately, and in particular, at the time point just before changing the polarity thereof. Thus, with an aid of additional supply of such the pulse-like current, it is possible to supply a predetermined power to the discharge lamp, and also at the same time, to suppress shifting of the position where the arc discharge occurs.
However, with the circuit apparatuses and the methods of the conventional technologies as were mentioned above, in particular, the Japanese Patent Laying-Open for International Application No. 2002-534766 (2002), the Japanese Patent Laying-Open for International Application No. 2002-532866, the Japanese Patent Laying-Open No. 2002-15883 (2002), and the U.S. Pat. No. 5,608,294, though the pulse-like current is additionally supplied onto the specific time portion of the lamp current, but at that instance, it is necessary to obtain an operation parameter of the high-pressure discharge lamp, such as, a parameter indicative of a distance between the electrodes, for example, for determining an amplitude of the pulse-like lamp current.
As an example of the parameter to be detected, for example, it is the lamp voltage between the respective ones during the continuous time period. Those can be detected by means of a microprocessor, which is provided within the circuit apparatus. In more details, it can be obtained by detecting the current flowing through an induction means of the converter.
In this manner, with the conventional technologies described in the Japanese Patent Laying-Open for International Application No. 2002-534766 (2002), the Japanese Patent Laying-Open for International Application No. 2002-532866, the Japanese Patent Laying-Open No. 2002-15883 (2002), and the U.S. Pat. No. 5,608,294, the distance between the electrodes is obtained, as being the operation parameter of the high-pressure discharge lamp, by means of the microcomputer, and the amplitude of the pulse-like lamp current is determined upon basis of the parameter obtained. For this reason, there is a further necessity of providing, such as, a current detector for detecting the current flowing through the inductance means of the converter, etc., for example. Accordingly, the number of parts of the lamp operation controller increases, or the apparatus itself becomes large in the sizes thereof, as well as, the manufacturing costs thereof.
In addition thereto, during use for a long time period of the high-pressure discharge lamp, there is a possibility that the parameter is detected erroneously, by means of the microcomputer through the current detector, due to the reason of noises generated within the lighting apparatus of the discharge lamp; i.e., the noises generated when the high voltage is produced before or after starting of lighting of the discharge lamp, etc. Further, in that instance, if the amplitude of the pulse-like lamp current is set to be a value larger than that necessary, for example, then it results into shortening of a lifetime of the high-pressure discharge lamp.